Microphones are used to obtain a voice signal from a speaker. Once obtained, the signal can be processed in a number of different ways. A wide variety of functions can be provided by today's microphones and they can interface with and utilize a variety of different algorithms.
Voice triggering, for example, as used in mobile systems is an increasingly popular feature that customers wish to use. For example, a user may wish to speak commands into a mobile device and have the device react in response to the commands. In these cases, a voice activity detector may first detect whether there is voice in an audio signal captured by a microphone, and then, subsequently, analysis is performed on the signal to predict what the spoken word was in the received audio signal. Various voice activity detection (VAD) approaches have been developed and deployed in various types of devices such as cellular phones and personal computers.
Microphones that are always on are often equipped with internal oscillators and operate at very low power. Low power microphones are used in various applications and sometimes two or more microphones are used when the device is brought out of the low power mode. Although the low power aspect allows some of the microphones to be on all the time in a low power listening mode, the microphones may also use buffers to aid in voice activity detection, which introduce processing delays. The processing delays may cause problems at the far end of the system where the signals frequently need to be processed as quickly as possible.
The problems of previous approaches have resulted in some user dissatisfaction with these previous approaches.
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